Signs and Symptoms of Hypoglycemia
Hypoglycemia presents with two distinct categories of symptoms: sympathetic/autonomic symptoms (sweating, tremor, palpitations, hunger, anxiety) and neuroglycopenic symptoms (confusion, altered mental status, weakness, slurred speech, lethargy, seizures, or coma), with severe hypoglycemia defined as requiring assistance from another person and often associated with mental status changes. 1
Definition and Thresholds
- Hypoglycemia is defined as blood glucose <70 mg/dL (3.9 mmol/L), which serves as the alert value for therapeutic intervention 1
- Clinically significant hypoglycemia occurs at <54 mg/dL (3.0 mmol/L), representing a threshold for serious physiological consequences 1
- Severe hypoglycemia is a medical emergency requiring assistance from a third party, often with altered mental status 1
Sympathetic/Autonomic Symptoms
These symptoms result from catecholamine release and typically appear first:
- Sweating (diaphoresis) - one of the most prominent early warning signs 1, 2, 3
- Tremor and shakiness 2, 3
- Palpitations and fast heart rate 2, 3
- Hunger sensation 2, 3
- Anxiety, restlessness, and irritability 2, 3
Neuroglycopenic Symptoms
These symptoms result from insufficient glucose supply to the brain and indicate more severe hypoglycemia:
- Altered mental status and confusion - a critical warning sign that should prompt immediate blood glucose checking 1
- Difficulty concentrating 2
- Blurred vision and visual changes 2, 3
- Weakness and lethargy 1, 3
- Slurred speech 2, 3
- Dizziness, lightheadedness, and vertigo 2, 3
- Headache 2
- Tingling of lips and tongue 2
- Drowsiness and somnolence 1, 2
Severe Hypoglycemia Manifestations
- Combativeness and agitation 1
- Incoherence 1
- Seizures 1
- Loss of consciousness and coma 1, 2
- Death if untreated 1, 4
Cardiovascular Manifestations
- Bradycardia can occur during hypoglycemic episodes, particularly nocturnal hypoglycemia, and may contribute to sudden death 5
- Atrial and ventricular ectopic beats occur more commonly during hypoglycemia 5
- QT prolongation has been documented in severe hypoglycemia 5
Critical Clinical Pitfalls
Warning symptoms may be diminished or absent in certain high-risk situations 2, 3:
- Long duration of diabetes reduces symptom awareness 2
- Diabetic autonomic neuropathy impairs counterregulatory responses 2
- Beta-blocker use masks tachycardia and other sympathetic symptoms 5, 2
- Intensified diabetes control lowers the threshold for symptom recognition 2
- Recent hypoglycemic episodes can cause hypoglycemia unawareness 1
Severe hypoglycemia symptoms can be confused with intoxication or withdrawal, making blood glucose measurement essential in any diabetic patient with altered mental status 1
Immediate Recognition Protocol
Any diabetic patient exhibiting altered mental status, agitation, and diaphoresis should have capillary blood glucose checked immediately 1. This triad is particularly concerning and should never be dismissed without glucose verification, as severe hypoglycemia can progress rapidly to seizures, coma, and death if untreated 1, 4.